Method Of Obtaining Measurement Data Using A Sensor Application Interface

ABSTRACT

A method involves, via a sensor application interface, 1) receiving, from an application, a measurement request associated with a quality-of-service control; 2) in accord with the quality-of-service control, obtaining measurement data from a sensor; and 3) returning to the application i) the measurement data obtained from the sensor, and ii) an indicator of accuracy of the measurement data.

CLAIM OF PRIORITY UNDER 35 U.S.C. §119

The present Application for patent claims priority to Provisional Patent Application No. 60/784,608 entitled “Sensor Application Interface” filed Mar. 20, 2006, assigned to the assignee hereof and hereby expressly incorporated by reference herein.

BACKGROUND

There are many sensors on the market today. These sensors are designed to convert a physical phenomenon into an electrical signal. For example,

Barometric Pressure Sensor

-   -   Measures atmospheric pressure         -   Altitude         -   Weather

Accelerometer

-   -   Measures direction of gravity         -   Linear movement         -   Tilt (Roll, Pitch)         -   Shock sensing         -   Free-fall

Gyroscope

-   -   Measures Coriolis effect         -   Heading Changes         -   Rotation

Magnetic Field Sensor

-   -   Measures direction of magnetic field         -   Compass         -   Absolute Heading

Accelerometers are the most widely used MEMS sensors with millions integrated into cars by the automotive industry. As said above, the linear accelerometers can sense the linear motion and can provide a measure of tilt. With a 3D accelerometer, motion in (x,y,z) can be sensed. In addition, the direction of the gravity can be used to estimate the roll (θ) and pitch (φ) (see FIG. 1).

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an illustration of a single-sensor accelerometer configuration;

FIG. 2 is an illustration of a two-sensor accelerometer configuration;

FIG. 3 is an illustration of linear movement of the two sensors shown in FIG. 2; and

FIG. 4 is an illustration of angular movement of the two sensors shown in FIG. 2.

DETAILED DESCRIPTION

Unfortunately, in wide number of cases it is difficult to differentiate between a linear motion (acceleration in x,y,z) and the change in the orientation of the device and the corresponding change in roll and pitch. Furthermore, a change in the heading (aka yaw or azimuth, ψ) can not be sensed by the linear accelerometers at all. For sensing the change in the heading, gyroscopes are commonly used. However, gyroscopes are expensive, large and complex structures and therefore more expensive than accelerometers.

What is needed is a solution which can reliably deliver a measure of linear motion and orientation. This invention discloses a method of integrating two 3D linear accelerometers in order to measure and provide 6D information (x,y,z,θ,φ,ψ), see FIG. 2. Since, accelerometers deliver second momentum the measurements need to be integrated once to get the rate of change and second time to get the absolute measures.

Two 3D accelerometers deployed at opposite corners of the board can sense the linear movement—sensors produce similar outputs (see FIG. 3), and sense orientation changes—sensors produce opposing outputs (see FIG. 4).

One key requirement is near simultaneous read-out of the measurements from both accelerometers.

In order to be able to efficiently use sensors in various applications, a sensor must provide several functions: control capability, measurement output and quality control.

An application programming interface (API) is defined which in addition to the control and common measurement output interface adds a quality control. The quality control has a bi-directional purpose. For example, on the input quality-of-service (QoS) control allows the sensor user (application developer) to prioritize the time per measurement vs. accuracy of the sensor measurement, it can specify how often the measurement is performed (periodic) and the duration of measurement period, define the event triggering the sensor measurement, threshold level for sensor output to trigger the measurement processing, length of measurement filtering (time constant), etc. The sensor QoS will add the accuracy measures to the raw measurement values: directional information accuracy, tilt accuracy, acceleration accuracy, rate of rotation accuracy, pressure accuracy, temperature accuracy, etc. It can also add specific event outputs such as “shock detected”, (e.g., acceleration magnitude above 1000 g was detected), etc.

The availability of sensor QoS control functionality facilitates sensor integration and allows successful integration of the measurements from multiple sensors for various applications utilizing sensor measurements. TABLE 1 Example Sensor Measurement Specification Measurement Data type Unit (resolution) Data range Geomagnetic Compass Direction 16-bit 0.1° 0 to 3599 angle signed (0° to 359.9°) integer Direction 4-bit 0 to 15° angle unsigned accuracy integer Magnetic 16-bit 0.1 μT −15000 to 15000 vector, signed (−1500 μT to 1500 μT) magnitude integer Magnetic 16-bit 0.1 μT −15000 to 15000 vector, x signed (−1500 μT to 1500 μT) integer Magnetic 16-bit 0.1 μT −15000 to 15000 vector, y signed (−1500 μT to 1500 μT) integer Magnetic 16-bit 0.1 μT −15000 to 15000 vector, z signed (−1500 μT to 1500 μT) integer Orientation angle Pitch 16-bit 0.1° −900 to 900 signed (−90.0° to 90.0°) integer Roll 16-bit 0.1° −1800 to 1800 signed (−180.0° to 180.0°) integer Orientation 4-bit 0 to 15° angle unsigned accuracy integer Linear Acceleration Acceleration 16-bit 0.1 mg −30000 to 30000 vector, signed (−3000 mg to 3000 mg) magnitude integer Acceleration 4-bit 0 to 10 mg accuracy unsigned integer Acceleration 16-bit 0.1 mg −30000 to 30000 vector, x signed (−3000 mg to 3000 mg) integer Acceleration 16-bit 0.1 mg −30000 to 30000 vector, y signed (−3 g to +3 g) integer Acceleration 16-bit 0.1 mg −30000 to 30000 vector, z signed (−3 g to +3 g) integer

The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein. 

1. A method, comprising: via a sensor application interface, receiving, from an application, a measurement request associated with a quality-of-service control; in accord with the quality-of-service control, obtaining measurement data from a sensor; and returning to the application i) the measurement data obtained from the sensor, and ii) an indicator of accuracy of the measurement data. 